Vehicle sprayers have been commonly used to spread liquids to large surface areas such as road surfaces and agricultural fields. Vehicle sprayers commonly have a tank that furnishes liquid to a sprayer manifold. In a typical sprayer manifold, a pump provides liquid through a network of hoses to arranged nozzles. Vehicle sprayers often include various control means which automatically or manually adjust the rate of flow to the nozzles. Pesticides, brine, oils, dust inhibitors, water and other liquid solutions and mixtures have been applied by vehicle sprayers.
Prior to this invention, vehicle spraying manifolds commonly comprised a horizontal bar configured with a large number of nozzles. The nozzles had one fixed orifice and a cone shaped or a V-shaped spray pattern. These nozzles were typically aligned perpendicular to the horizontal bar and directed at the ground. U.S. Pat. No. 4,817,870 assigned to Etnyre Co., the present assignee, shows a typical horizontal bar spraying apparatus and a method of achieving a uniform application rate for varying vehicle speeds and flow rates.
A problem associated with the horizontal bar configuration is that the swath of land sprayed by the vehicle is limited to the length of the bar. This limits coverage of land to the length of a short horizontal bar when obstacles exist in the path of the spray bar such as other vehicles, road signs, trees, or fences. However, horizontal bars have been used with a fixed orifice nozzle because of the many difficulties and variables inherent with vehicle sprayers and because it is highly desirable to provide uniform application of the liquid to the land surface.
One difficulty is that a vehicle sprayer often varies its speed while spraying. On board computers have adjusted the flow rate according to the vehicle speed. Another difficulty is that wind or turbulence created by movement of the vehicle has not allowed for uniform distribution of smaller liquid particles, especially at long trajectories. An additional difficulty is that nozzles are often fed liquid from the same manifold and pump, which requires balancing of flow rates among several nozzles.
Mounting vehicles with vertical manifolds that spray outside the width of the horizontal bar have not traditionally existed because of the limits associated with fixed orifice nozzles. For nozzles mounted to spray outside the width of the bar, nozzles are inclined relative to the ground. Nozzles are not aligned vertically and are not equidistant to the land surface. Despite the wide range of spray trajectories and liquid particle sizes available, fixed orifice nozzles have not allowed vehicles to spray uniformly outside the span of the bar.
Inclined fixed orifice nozzles have had significant problems when flow rate is varied. Resulting problems include a non-uniform trajectory distance and a changing liquid particle size in the discharged liquid. In fixed orifice nozzles, increasing flow rate has rapidly increased the fluid pressure inside the fixed orifice nozzle and thus increased the velocity of the discharged liquid. Changes in liquid velocity change the land surface reached by a nozzle, thus unevenly distributing liquid. The increasing fluid pressure also has caused discharged liquid particles to atomize or diminish in size. Wind and vehicle turbulence affect the smaller particles, causing uneven distribution to the land surface. The rapid changes in discharge velocity and particle size have limited the range of flow rates and thus the vehicle speeds over which inclined nozzles provide uniform liquid application to the land surface.
Simple nozzles that automatically adjust to provide a uniform trajectory and particle size for varying rates of flow when mounted severally in vehicle sprayers have not traditionally existed. Nozzles exist in other applications that adapt the orifice size based on the rate of flow. The broad concept of a spring-loaded variable flow rate nozzle is disclosed in several U.S. patents. For example, U.S. Pat. No. 3,539,112 discloses a fire hose nozzle, which includes a selected flow-regulating means in the form of a spring acting to axially bias the valve head in opposing relation to the water pressure. U.S. Pat. No. 3,742,701 discloses a liquid propellant injector having a spring-biased valve to produce a uniform spray pattern. Finally, U.S. Pat. No. 2,229,467 discloses a spring-loaded nozzle that is intended to discharge liquids carrying solid matter without clogging. U.S. Pat. No. 3,684,192 discloses a constant pressure, variable flow nozzle with two variable orifices, for use in fire fighting applications.
Because of the shortcomings of fixed orifice nozzles, and prior to this invention, the present assignee developed a nozzle with one variable orifice. The variable orifice automatically increased the flow path area to spray a stream-like fan pattern over a much wider range of flow rates than traditional fixed orifice nozzles. The variable orifice nozzle comprised a solid spherical poppet variably retained by a spring adjacent to a circular discharge port of the nozzle.
When the variable orifice nozzles were mounted inclined relative to the ground, liquid flowed around the poppet in a stream-like fan pattern and struck the land surface, spreading out in a predictable pattern. These nozzles were fluidically connected in the same manifold. The nozzles were mounted on a horizontal bar and two verticals arms of a vehicle sprayer manifold. The horizontal bar discharged liquid to a lane of road immediately behind the vehicle. The vertical arms sprayed two additional lanes, one lane on each side of the vehicle. A computer adjusted the flow rate to the nozzles according to vehicle speed.
An exemplary and significant application for the vehicle sprayer was spraying brine solution in cold weather to de-ice the road surface. By spraying liquid brine to a roadway surface, ice and snow was more quickly de-iced or liquidized which increased roadway safety. The variable orifice nozzle worked well for a wide range of higher vehicle speeds and higher flow rates. The vehicle sprayer could reach areas that previously could not be reached by other prior art vehicle sprayers because obstacles did not restrict movement or spraying of the vehicle. The vehicle sprayer could also spray multiple roadway lanes which decreased the number of unsprayed lanes.
However, the vehicle sprayer with only one variable orifice had problems. The variable orifices of the multiple nozzles fed from the same manifold did not open up equally at low vehicle speeds and low flow rates to provide uniform liquid application. When sprayer vehicles slowed down, for example to enter an intersection, vehicle speed decreased and thus flow rate decreased as well. At low flow rates, liquid flowed through only some or one of the nozzles, resulting in non-uniform liquid application. Intersections have been an important area to de-ice to prevent accidents as other vehicles stop or accelerate there. With liquid brine flowing out only some or one of the nozzles, non-uniform de-icing of the road surface had occurred.
The uniformity problems depended on how well the springs in the nozzles were balanced and how many nozzles were actively discharging liquid. For roadway spraying applications, uniformity problems had occurred at liquid applications below 20 gallons per minute. At 10 gallons per minute, the liquid typically only flowed through some nozzles, while flow through other nozzles would be completely lost. As flow rate decreased to 5 gallons per minute or less, liquid typically only flowed through 1 nozzle in the entire sprayer manifold. In terms of vehicle speeds for de-icing applications, uniformity problems as to de-icing applications occurred at flow rates corresponding to vehicle speeds of 5 miles per hour and less.